The present invention is directed generally to waveform processing oscilloscopes, and more particularly to a raster scan display system for use in such instruments.
In digital type oscilloscopes, an applied analog signal is first converted to a digital signal, the digital signal is stored and/or mathematically processed, and the processed signal is reconverted to an analog signal for display by a cathode ray tube. Such digital oscillscope instruments are particularly well suited for displaying complex signal waveforms where measurements and calculations on selected portions of the waveforms must be performed to provide waveform and numerical output displays indicative of selected parameters of the waveforms. In this regard, digital oscilloscope instruments have the flexibility of providing a wide range of storage, display and processing options, including one-half and one-quarter screen displays and graphics and multiple step processing programs.
To provide a desired output display in digital oscilloscope instruments it is necessary that waveforms and other data to be displayed be read into discrete locations in a memory array. The memory array is then read out location-by-location into a CRT, which is scanned in synchronism with the readout. Where it was required to shift the position of one or more waveforms on the display, it was necessary in prior oscilloscope constructions to shift the data from one location to another in the memory array. This was often a time-consuming operation which interfered with other processing operations in the instrument CPU.
A preferred construction for the display system of a digital oscilloscope, which avoids the need to shift data by providing three discrete simultaneously-read display planes, is shown in the copending application of John R. Figie, "Digital Waveform Processing Oscilloscope with Multiple Plane Display System", Ser. No. 567,225, filed concurrently herewith and assigned to the present assignee. The present invention is directed to a data distribution system for use in this construction whereby data is distributed within the display planes in accordance with the difference between the data acquisition rate and the display rate to provide optimum definition of an acquired waveform in the display.
A preferred calibration system for use in the oscilloscope is shown in the copending application of Terry Schwalenberg, "Digital Waveform Processing Oscilloscope with Automatic Calibration System", Ser. No. 567,092, filed concurrently herewith and assigned to the present assignee.